i can not upgrade my mac os to mavericks

Why not? What has happened when you tried? What exact model Mac do you have and how is it configured? What version of OS X do you now have installed?

<OS X Mavericks: System Requirements>

The following are ways to identify which Mac you have:

<http://www.everymac.com/ultimate-mac-lookup/>

<http://www.powerbookmedic.com/identify-mac-serial.php>

<How to identify MacBook Pro models>

Off hand I would say you have run into some server-side issue. Try this:

Repair the Hard Drive and Permissions - Mavericks, Lion/Mountain Lion

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair

When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu. Select Restart from the Apple menu.

Open App Store and sign in with your Apple ID and try the download once more. There is nothing you can do if there is a server-side problem but wait for Apple to fix it.